For a long session with multiple orgasms I get a length of cotton (about 2 feet) and make a loop in the middle. I get my clit hard (it's quite large & sticks out a bit when I'm excited) and close the loop around the head of my clit. Then I simply tug very gently using a slowly increasing rythm. I find this gives guaranteed orgasms-as many as I can handle.

For a really powerful orgasm, I get a yard of 1/2' diameter rubber tubing that I bought especially and, with plenty of lubrication, place the end over my clit. By applying suction rythmically and sucking hard at the crucial moment, I can have my most powerful orgasms, only 1 at a time with this method though. It makes my clit rather numb.